The process of wire-cutting electroerosion makes use of a continuous wire electrode of a thickness in the range between 0.05 and 0.5 mm.phi. which is axially advanced and transported from an inlet side through a cutting zone to an outlet side. In the cutting zone there is positioned a workpiece and a machining gap is formed between the advancing or traveling wire electrode and the workpiece. A machining liquid, typically distilled water of dielectric nature or a liquid electrolyte, is supplied to fill and flush the machining gap while an electric current, advantageously in the form of a series of pulses, is applied between the wire electrode and the workpiece to create a succession of electrical discharges or a strong electrolytic action through the fluid medium, thereby allowing material to be removed from the workpiece. As material removal proceeds, the workpiece is displaced relative to the axially traveling-wire electrode generally transversely to the axis thereof along a prescribed cutting path to form a desired cut in the workpiece.
In the path of wire travel, drive rollers driven by a motor are typically provided in the outlet side to apply a traction force to the wire electrode to feed it at a predetermined rate of advancement. Brake rollers driven by a motor may further be provided in the inlet side. Thus, the wire electrode is capable of traveling stretched under a suitable tension along the path, which should also include a pair of guide members constituted with smooth arcuate bearing surfaces designed to change the direction of wire travel from the inlet side to the cutting zone and from the latter to the outlet side, respectively. These guide members may also serve as wire-positioning guides to precisely align the traveling-wire electrode in a predetermined machining position across the workpiece in the cutting zone.
The structure of a wire-positioning guidance member therefore directly influences the machining accuracy which ensues.
Heretofore, three forms of the wire passage in the wire guidance and support assembly have been commonly in use. One makes use of a pin around which the wire electrode is carried and the second employs a V-shaped notch either rectilinear or arcuate providing a bearing surface for the traveling wire electrode. These forms tend to cause the traveling wire to come off, thereby giving rise to machining inaccuracy. The third form makes use of a die or an internal passage formed through an elongated solid member but such a structure does not allow easy mounting and dismounting of the continuous wire electrode.